Silicon-carbid article and method of making the same.



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No Drawing.

To all whom. it may concern." Be it known thatwe, Enmmu and Fauna J. Tons,

, SI Siurrn residents of Niagara Falls, in the'county of Niagara and Stateof' New York, have invented "a' new andus'eful Improvement in Silicon-Carbid Articles and Methods of Making the Same,of which the following'is a full, clear, and exact description.."

Our invention-relates -to silicon carbid articles, particularly those usedas refractory material or el'ectrioresistances It has lon been known that silicon carbid possesses va uable' refractory properties; but

its" low thermalresisti'vity makes it a fairly good conductor and thus prevented its entrance intoj'alaige tield'of usefulness.-

Our invention is' desi this diiiiculty and to ve a new silicon carbid material WlliClLWl l have a hi her resistance to heat conduction and is t erefore valuable for refractory purposes as well as for electrical-resistance devices and other uses.

We have discovered that when porous carbonaceousf'materiahg as for ,example' carbonized wood is treated with". silicon containing va era, the carbonisconyerted'inieitu into and if the tem erature is not carried too h too'lon the silicon'earbld so formed --will retain t is physical structure and porosity of i I the orifiginal carbon structure, giving it new and va uable properties.

In carryin out our process in a referred form, we ta e a mixture of the ollowing constituents by weight: 80 parts pulverize coke, 00 arts silica sand and 10 parts sawdust. T is mixture is laced in an electric furnace, preferabl of egranular core resistance type well nown in the manufacture of silicon carbid and such as shown in the U. S. Patent No. 560,291, granted on May 19, 1896 to E. G. Acheson.

Blocks or pieces of wood are buried in andv entirely surrounded b being placed refersb y at a distance of from 2 to 8 in es from the core. The furnace is then. operated in the-"ordinarymay the mixture, this em loyedin themanufacturej'of silicon carbid *sroundfthe-jcore a- Ja l-t e e s fqrmed zone",of'--crystalline silicon carbid; which ex tendsoutwardlyto;- thepoints- 'where the blocks of wood are plac but does-not in 1. amass at Litterretest s ueaueaante nae, sm; serial No. seas-1a.

ed to overcome gh nor the reac ion continued hlude them. Under these conditions the wood is first'thoroughly carbonized and the volatilized silica or other silicon-containing, combined vapors circulating freely throu h the porous mixture then re-act with the orous carbonto convert itinto silicon carid of very high and uniform lporosit without materially chan ing the s iape physical structure or general exture. It 18 important that the temperature shall not be carried too high and that the silicidizing action shall not be too long continued, since if these conditions are not carried out, the carbon will be chan ed into a dense form of silicon carbid' lac ing the peculiar qualities of the grade we are able to produce.

The orous silicon carbid article thus 'produced s ows no crystalline formation to the naked eye or even under a microscope of low power. If crystals exist, as is possible, they are of microscopic size; and the product appears to be amorphous.

In color the product is generally of a light, delicate reen; in porosity and texture it resem les charcoal. A typical was em;

- Siliooncarbid -i a. 00 Free silica. 2. 44 Iron and aluminum oxide" 1. 50

The product has the same chemical properties as ordinary crystalline carbid except that it is more susce tible to oxidation at high temperatures. t has about the same specific gravity as crystalline silicon carbid; but its apparent density is about 0.27 rams 'per cubic centimeter, which is well )elmv that of anyform of silicon carbicl hcrctofore produced. This apparent density is always below 0.40. The material has spcciul application as a refractory, combining to a degree that no other substance does, a high resistance to fusion and a high resistance to heat conduction. It is a oor conductor of eleotricit and can be use for example, in elect-rice. resistance devices. Owing to its ultimate-fineness of particle and its uniform porous nature, it is a very oor conductor of 1 eatand'this property-ma es it valuable as a heat insulating material.

Instead of using blocks of wood other nmterials may be used, such as cotton, paper,

Patented Apr. 15,1913.

till

ulp, cellulose, lamp-black, coke and other substances may be used which have, in the carbonized statc,a porous or finely divided structure or texture- With many such carbon-containing materials it is possible to produce similar forms of porous silicon carnd possessingbthe valuable roperties of the silicidized car on produced rom the wooden blocks. as above described.

Many changes may be made in the form and arrangement of the furnace, the method of subjecting the carbon article to Siliconcontainin vapors, etc., without departing from our invention.

We claim:

1. As a new article of manufacture, porous silicon. carbicl which is non-crystalline under naked vision and is characterized by extreme fineness of particle and pore,

2. As a new article of manufacture, porous silicon carbid non-crystalline under naked vision, and of uniform porosity and low apparent density, said article being characterized by extreme fineness of particle and pore.

3. As a new article of manufacture, orous silicon carbid in masses'of substantial y uniform porosity, characterized by extreme fineness of particle andpore, said masses having an apparent densit of less than QAQ.

4. As a; new artic e of manufacture, porous silicon earbid, non crystalline undernaked vision, and having'an apparent density of less than 0.40.

5. As a new article of manufacture, silicidized carbon non-crystalline under naked vision of uni orm orosity and low a parent density, said artic e bein extreme fineness of partic e and-pore.

6. As a new article of manufacture, porous characterized by silicon car-bid having a high resistance to heat conduction, said article bcin characteriaed b extreme fineness of partie 0 and ore.

7. he method of making porous si icon carbid, consisting in subjecting porous carin bonized matter to silicon-containing vapors at a temperature which converts the carbon into porous silicon carbid non-crystalline under naked vision.

8. The. rocess of making porous silicon ctllbid, w ich consists in subjecting curbonaceous matter which is porous after carbonization, to silicon-containing vapors at a temperature sufiicient to convert the carbon into porous silicon carbid, non-crystalline under naked vision, but insullicient to convelt it into dense silicon carbid or silicon carhid of a plainly crystalline formation.

9.. The process of making a shaped porous Silicon carbid article which consists in forming -a similarly sha d article of carbonaceous. matter, whic is porous after carbonization, subjecting said carbon articles to silicon-containing vapors at a temperature sufficient to convert the article into porous silicon carbid corresponding in texture and porosity to the carbonized article, but insuflicient to convert it into dense or plainly e stalline silicon carbid.

,n testimony whereof, we have hereunto o \Vitnesses as to Edmund S. Smith: O'ns Ho'rcnms,

ROY Lmcomr.

Witnesses as to Frank J. Tone:

' EARL H. Fmmcoan,

J, Raruss.

m copies or thin patent my be obtained for in mm on, by Arming the oommluloncr of Patents, Wllhlagton, D. 0." 

